Bifurcated endoluminal prosthesis

ABSTRACT

An introducer for delivering into the vasculature a straight or bifurcated stent or prosthesis; a method for delivering into the vasculature a straight or bifurcated stent or prosthesis; a method of treating and angeological disease using a bifurcated stent; an endoluminal stent having perpendicular hoop members, each hoop member formed of wire in a sinuous configuration, at least some of juxtaposed apices in neighboring hoops being secured to one another, such stents also forming axially aligned segments in straight stents, and segments of bifurcated stents in particular embodiments. Certain embodiments of such stents also include barbs, fabric covering and radiopaque markers.

This application is a division of application Ser. No. 08/317,763, filedOct. 4, 1994, now U.S. Pat. No. 5,609,627, which is aContinuation-in-Part of application Ser. No. 08/312,881, filed Sep. 27,1994.

BACKGROUND OF THE INVENTION

The present invention relates to a bifurcated endoluminal prosthesis foruse in a bifurcated blood vessel such, for example, as the infrarenalportion of a mammalian aortic artery where it bifurcates to the commoniliac arteries. The present invention also embraces a stent connectingmeans for connecting a stent (e.g. a stent which forms part of anendoluminal prosthesis) to another stent, as well as apparatus andmethod for introducing prostheses to the vasculature and methods oftreating angeological diseases.

A stent is used to provide a prosthetic intraluminal wall e.g. in thecase of a stenosis to provide an unobstructed conduit for blood in thearea of the stenosis. An endoluminal prosthesis comprises a stent whichcarries a prosthetic graft layer of fabric and is used e.g. to treat ananeurysm by removing the pressure on a weakened part of an artery so asto reduce the risk of embolism, or of the natural artery wall bursting.Typically, a stent or endoluminal prosthesis is implanted in a bloodvessel at the site of a stenosis or aneurysm by so-called "minimallyinvasive techniques" in which the stent is compressed radially inwardsand is delivered by a catheter to the site where it is required throughthe patient's skin or by a "cut down" technique in which the bloodvessel concerned is exposed by minor surgical means. When the stent ispositioned at the correct location, the catheter is withdrawn and thestent is caused or allowed to re-expand to a predetermined diameter inthe vessel.

U.S. Pat. No. 4,886,062 discloses a vascular stent which comprises alength of sinuous or "zig-zag" wire formed into a helix; the helixdefines a generally cylindrical wall which, in use, constitutes aprosthetic intraluminal wall. The sinuous configuration of the wirepermits radial expansion and compression of the stent; U.S. Pat. No.4,886,062 discloses that the stent can be delivered percutaneously andexpanded in situ using a balloon catheter.

U.S. Pat. No. 4,733,665 discloses an expandable intraluminal graft whichis constituted by a tubular member formed from a plurality ofintersecting elongate members which permit radial expansion andcompression of the stent.

EP-A-0556850 discloses an intraluminal stent which is constituted by asinuous wire formed into a helix; juxtaposed apices of the wire aresecured to one another so that each hoop of the helix is supported byits neighboring hoops to increase the overall strength of the stent andto minimize the risk of plaque herniation; in some embodiments the stentof EP-A-0556850 further comprises a tubular graft member to form anendoluminal prosthesis.

The prior art stents and prostheses mentioned above are generallysatisfactory for the treatment of aneurysms, stenoses and otherangeological diseases at sites in continuous unbifurcated portions ofarteries or veins.

However, the prior art stents and prostheses are not wholly satisfactoryfor use where the site of desired application of the stent or prosthesisis juxtaposed or extends across a bifurcation in an artery or vein such,for example, as the bifurcation in the mammalian aortic artery into thecommon iliac arteries. For example, in the case of an abdominal aorticaneurysm ("AAA") in the infrarenal portion of the aorta which extendsinto one of the common iliac arteries, the use of one of the prior artprosthesis referred to above across the bifurcation into the one iliacartery will result in obstruction of the proximal end of the othercommon iliac artery; by-pass surgery is therefore required to connectthe one iliac artery in juxtaposition with the distal end of theprosthesis to the other blocked iliac artery. It will be appreciated bya person skilled in the art that it is desirable to avoid surgerywherever possible; the requirement for by-pass surgery associated withthe use of the prior art prosthesis in juxtaposition with a bifurcationin an artery therefore constitutes a significant disadvantage.

SUMMARY OF THE INVENTION

Throughout this specification, the term "proximal" shall mean "nearestto the heart," and the term "distal" shall mean "furthest from theheart."

According to one aspect of the present invention there is provided astent connecting means for connecting two intraluminal stents one to theother to define a continuous lumen through the two stents, the stentconnecting means including a first stent including a male engagingportion which can be compressed radially inwardly, and a second stentincluding a female cooperating portion. The male engaging portion may beentered into the female cooperating portion in a radially compressedstate and thereafter caused or allowed to expand in the femalecooperating portion; the arrangement being such that in service theinterengagement of the male engaging portion and the female cooperatingportion serves to resist longitudinal separation of the two stents onefrom the other.

Typically, the first stent may include a proximal male engaging portion;the second stent may include a distal female cooperation portion. Themale engaging portion may be flared radially outwardly towards itsextremity, and the female cooperating portion may be tapered radiallyinwardly towards its extremity. In some embodiments, the male engagingportion may comprise a frustoconical wall which flares outwardly towardsits longitudinal extremity; the female engaging portion may comprise afrustoconical wall which tapers radially inwardly towards itslongitudinal extremity.

Alternatively, said male engaging and female cooperating portions may besubstantially untapered; they may be substantially cylindrical.

The male engaging portion of the first stent may be resilientlycompressible in a radially inwards direction such that in the radiallycompressed state it is capable of self-reexpansion to engage in thefemale cooperating portion. Typically, each of said first and secondstents may be resiliently compressible.

In use therefore the second stent may be delivered in a radiallycompressed state by using a catheter; when the second stent is locatedat the site of use, the catheter may be withdrawn thereby allowing thesecond stent to re-expand to engage the endoluminal surface of the bloodvessel.

The first stent may then be delivered percutaneously or by a "cut down"technique to a site distal of the second stent such that the mateengaging portion of the first stent in the radially compressed state isentered into the expanded female cooperating portion of the secondstent; the catheter may then be withdrawn allowing the first stent tore-expand such that the male engaging portion engages in the femalecooperating portion of the second stent.

In some embodiments of the present invention the second stent may havetwo transversely spaced distal female cooperating portions; the secondstent may therefore constitute a bifurcated stent for use injuxtaposition with a bifurcation in a blood vessel.

Each of the two transversely spaced distal female cooperating portionsmay be adapted for connection to a first male stent which, in use,extends across the bifurcation into a respective one of the branchedblood vessels.

In a particular aspect of the present invention there is provided abifurcated intraluminal stent for use in juxtaposition with anangeological bifurcation; the bifurcated intraluminal stent comprising aproximal portion adapted to be positioned in service in a blood vesselin juxtaposition with a bifurcation, a first distal stent portionadapted to extend across the bifurcation into one of the branched bloodvessels and a second distal stent portion adapted to allow blood to flowfrom the proximal portion into the other branched vessel. The firstdistal stent portion may be formed integrally with the proximal portion.

In some embodiments the second distal stent portion may comprise afemale cooperating portion which is adapted to engage a male engagingportion of a another stent adapted to extend in the other branched bloodvessel such that, in use, the bifurcated stent can be connected in situto the other stent. The bifurcated intraluminal stent may thereforeconstitute a second stent in accordance with the present inventioncomprising a distal female cooperating portion disposed intermediate theproximal and distal extremities of the stent; the other stent mayconstitute a first stent in accordance with the present invention.

Typically, the proximal end of said second stent may be flared radiallyoutwardly towards its extremity to engage the endoluminal surface of theartery thereby to resist longitudinal movement of the second stent inservice.

Each of the first and second stents may comprise a sinuous wire formedinto a tubular configuration. The sinuous and tubular configurations maybe imparted to the wire by winding it on a mandrel. Typically, eachstent may be made from a shape memory nitinol (nickel-titanium) wirewhich may be wound on to the mandrel to form the stent in a tubularconfiguration of slightly greater diameter than the diameter of theblood vessel in which the stent is intended to be used. The stent may beannealed at an elevated temperature and then allowed to cool in air sothat the nitinol wire "remembers" the configuration in which it waswound on the mandrel.

Said nitinol wire may be type "M" nitinol wire which is martensitic attemperatures below about 13° C. and is austenitic at temperatures aboveabout 25° C.; it will be appreciated therefore that the type "M" wirewill be austenitic at body temperature of 37° C. Typically, theannealing may be conducted at about 500° C. or more for at least about60 minutes; after cooling the wire may be immersed in cold water tofacilitate removal of the wire from the mandrel with the wire in itsmaleable martensitic form. Typically, the cold water may havetemperature of less than about 10° C.; the wire may be immersed forabout 5 minutes or more. An advantage of using nitinol wire to form thestent in accordance with the present invention is that the nitinol wireis "super elastic" in its austenitic state; the radial outward forceexerted by the stent on the wall of the blood vessel in use is thereforesubstantially constant irrespective of the diameter of the vessel andthe expanded stent.

In some embodiments the wire may have a helical configuration asdisclosed in EP-A-0556850. Alternatively, the wire may be of an entirelynovel configuration, namely one in which the wire forms a plurality ofhoops such that the plane of the circumference of each hoop issubstantially perpendicular to the longitudinal axis of the stent. Eachhoop may comprise a substantially complete turn of the wire having asinuous configuration; optionally, as each hoop is completed, the pointof winding the wire may be displaced longitudinally with respect to thewinding axis to form the next hoop. When the next hoop is complete, thepoint of winding is moved further longitudinally with respect to thewinding axis to the form the next succeeding hoop and so on.

It will appreciated that an advantage of this novel arrangement is thatthe planes of the hoops are not skewed with respect to the longitudinalaxis of the stent; the longitudinal ends of the stent are "square" tosaid longitudinal axis, so that when the stent is caused or allowed toexpand in situ there is substantially no twisting of the stent as itshortens in length. It will be appreciated that this represents asignificant advantage, as in areas of stenosis or aneurysm it isdesirable to minimize the movement of the stent within the blood vesselso as to reduce the potential trauma to the patient. A stent of thisconfiguration may be used, apart from the bifurcated embodimentotherwise taught herein, in any application which in stents generallyhave heretofor been used.

Typically, the stents of this invention whether of the helical orperpendicular variety, also comprise a securing means for securing anapex of the sinuous wire in one hoop to a juxtaposed apex of aneighboring hoop so that each hoop is supported by its neighbors. Thesecuring means may comprise a loop element of a suture material, forexample, to tie the juxtaposed apices together; the loop element mayalso comprise a loop formed of a thermoplastics material such, forexample, as polypropylene. Alternatively, the securing means may be abead formed of a thermoplastic material around juxtaposed apices. Alsoalternatively, the securing means may be a loop, ring, or staple formedof wire such as nitinol.

The male engaging portion and female cooperating portion, of the firstand second interengaging stents of this invention, may be formedseparately from the remainder of the respective non-engaging portions ofthese stents and then the engaging and non-engaging portions secured toone another by securing means.

In one embodiment of the present invention, the proximal and distalstent portions of the bifurcated stent in accordance with the presentinvention may be formed separately; the distal end of the proximal stentportion may be secured to the wider proximal end of a first intermediatefrustoconical stent portion; the narrower distal end of the firstintermediate frustoconical stent portion may be secured to the proximalend of the distal stent portion. The female cooperating portion of thebifurcated stent may be constituted by a second frustoconical stentportion which is secured to the distal end of the proximal stent portionin juxtaposition with the first frustoconical portion.

Alternatively the first and second frustoconical portions may beomitted; the proximal and distal stent portions may be secured directlyone to the other.

The female cooperating portion may be constituted by a generallycylindrical stent portion secured to said proximal stent portion intransversely spaced relation to the distal portion.

Each of the first and second stents of the bifurcated form of thepresent invention may carry a tubular graft layer formed from abiocompatible fabric in juxtaposition with the stent; the combined stentand graft layer constituting an endoluminal prosthesis. Typically thegraft layer may be disposed externally of the stent; it will beappreciated however that in some embodiments the graft layer may bedisposed internally of the stent. In some embodiments the graft layermay be secured to the stent by loop elements such, for example, as loopsof polypropylene. The biocompatible fabric may be a polyester fabric ora polytetrafluoroethylene fabric; typically said fabric may be woven ora warp knitted polyester fabric. In some embodiments the woven or a warpknitted fabric may be formed in a seam-free bifurcated configuration asa sleeve for a bifurcated stent.

In some embodiments the male engaging portion of the first stent and thefemale cooperating portion of the second stent may be left uncovered.Alternatively, the fabric graft layer may extend to the proximalextremity on the external surface of the male engaging portion, and maybe folded over the distal extremity of the female engaging portion toform an inner sleeve; in use the external fabric of the male engagingportion may butt against the folded over portion of the fabricinternally of the female cooperating portion to form a substantiallyblood tight seal.

The present invention in one aspect therefore includes a bifurcatedendoluminal prosthesis comprising a bifurcated stent in accordance withthe invention and a tubular graft layer.

The first stent having the male engaging portion may also have a tubulargraft layer. If required the first prosthesis may be introduced in aradially compressed state such that the male engaging portion of thefirst prosthesis is engaged in the intermediate female cooperatingportion of the bifurcated prosthesis; the first prosthesis is thencaused to be allowed to re-expand in situ such that the male engagingportion engages in the female cooperating portion to resist longitudinalseparation of the two prosthesis in service.

The bifurcated prosthesis may be adapted for use in the infrarenalportion of a mammalian aorta in juxtaposition with the bifurcation ofthe common iliac arteries for the treatment of abdominal aorticaneurysms. In use the bifurcated endoluminal prosthesis may beintroduced into the infrarenal portion of the aorta using a cathetersuch that the first distal stent portion extends into one of thebranched iliac arteries; the catheter may then be withdrawn allowing theprosthesis to re-expand in situ.

It will be appreciated by a person skilled in the art that theprostheses may be introduced to the site of use percutaneously or by"cut down" techniques.

Any of the stents according to this invention may be provided on itsexternal surface with circumferentially spaced wire barbs or hooksadapted to engage in the endoluminal surface of the host artery toresist longitudinal movement or slippage of the stent in use. Typicallythe barbs or hooks may be disposed on part of the stent which isprovided with a fabric graft layer such that in use the points of theartery which are engaged by the barbs or hooks are covered by the fabricgraft. It will be appreciated by a person skilled in the art that thetrauma to the artery wall caused by the hooks or barbs may cause emboli;the provision of the fabric graft over the barbs or hooks in use willtherefore help to prevent the introduction of such emboli into the bloodstream.

The male engaging portion for the first stent may be provided withcircumferentially spaced hooks or barbs on its external surface toengage the internal surface of said female cooperating means, thereby toreinforce the connecting means against longitudinal separation of thestents one from the other in the service.

The present invention therefore provides a connecting means forconnecting two stents longitudinally one to the other. It will beappreciated that this represents a significant step forward in the artas it allows the provision of a bifurcated endoluminal prosthesis foruse in juxtaposition e.g. with arterial bifurcations without requiringby-pass surgery to connect one of the branched arteries to the otherbranched artery.

In particular, the invention provides a bifurcated endoluminalprosthesis which can be positioned in an artery in juxtaposition with abifurcation to extend into one of the branched arteries; the bifurcatedprosthesis can be connected to another prosthesis which extends into theother branched artery. The prosthesis can be delivered percutaneously orby "cut down" methods and connected together in situ thereby to provideeffective treatment of an angeological disease such, for example, as ananeurysm or a stenosis which extends across a bifurcation in a bloodvessel without the need for by-pass surgery.

In another aspect, this invention provides an introducer for delivering,into the vasculature at an angeological bifurcation where a blood vesselbranches into two branched vessels, a bifurcated endoluminal stent orprosthesis having a proximal portion adapted to be disposed in the bloodvessel and a distal portion adapted to be disposed at least partially inone of the two branched vessels. The introducer comprises a tubularouter sheath, a proximal portion pusher disposed at least partiallywithin the outer sheath, and a distal portion pusher disposed at leastpartially within the proximal portion pusher.

The present invention further provides an introducer for delivering intothe vasculature at an angeological bifurcation where a blood vesselbranches into two branched vessels, an endoluminal prosthesis having aproximal stent portion and a distal stent portion. The introducercomprises a tubular outer sheath, a proximal portion pusher disposed atleast partially within the outer sheath and having a proximal endadapted to contact the proximal stent portion, a distal portion pusherdisposed at leant partially within the proximal portion pusher andhaving a proximal end adapted to contact the distal stent portion; and aballoon catheter, having a balloon attached thereto, disposed at leastpartially within the distal portion pusher.

This invention in another aspect provides a method for delivering abifurcated endoluminal stent or prosthesis having a proximal portion anda first distal portion into the vasculature at an angeologicalbifurcation where a blood vessel branches into a first branched vesseland a second branched vessel. The method comprises inserting a firstintroducer containing the stent or prosthesis into the vasculature to apredetermined delivery location, the first introducer comprising anouter sheath, a proximal portion pusher, and a distal portion pusher;withdrawing the outer sheath of the first introducer while maintainingthe proximal portion pusher in a fixed position until the proximalportion of the stent or prosthesis is deployed from the first introducerinto the blood vessel; withdrawing the outer sheath and the proximalportion pusher while maintaining the distal portion pusher in a fixedposition until the first distal portion of the stent or prosthesis isdeployed from the first introducer at least partially into the firstbranched vessel; and withdrawing the first introducer from thevasculature.

This invention further provides a method for delivering, into thevasculature at an angeological bifurcation where a blood vessel branchesinto two branched vessels, an endoluminal prosthesis having a proximalstent portion, and a distal stent portion. The method comprises thesteps of inserting an introducer containing the prosthesis into thevasculature to a predetermined delivery location, the introducercomprising an outer sheath, a proximal stent portion pusher, a distalstent portion pusher, and a balloon catheter having a balloon attachedthereto; inflating the balloon to at least partially block blood flow inthe blood vessel; withdrawing the outer sheath of the introducer whilemaintaining the proximal stent portion pusher in a fixed position untilthe proximal stent portion of the prosthesis is deployed from theintroducer into the blood vessel; withdrawing the outer sheath and theproximal stent portion pusher while maintaining the distal stent portionpusher in a fixed position until the distal stent portion of theprosthesis is deployed from the introducer into the blood vessel; andwithdrawing the introducer from the vasculature.

In general, this invention provides a method of treating an angeologicaldisease at a bifurcation site where a blood vessel branches into a firstbranched vessel and a second branched vessel comprising the steps ofdisposing in the blood vessel a proximal portion of an endoluminalstent; directing blood flow from the blood vessel into the firstbranched vessel through a first distal portion of the endoluminal stent,the first distal portion being connected to the proximal portion andextending into the first branched vessel; and directing blood flow fromthe blood vessel into the second branched vessel through a second distalportion of the endoluminal stent, the second distal portion beingconnected to the proximal portion and extending into the second branchedvessel. This method may be applied to aneurysms, occlusions, orstenosis.

Following is a description by way of example only and with reference tothe accompanying drawings of the present invention, including novelstent constructions and methods of manufacture and use thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects, features and advantages of the present invention will bemore readily understood from the following detailed description whenread in conjunction with the accompanying drawings, in which:

FIG. 1a is a front view of a bifurcated intraluminal stent in accordancewith the present invention constituting part of an endoluminalprosthesis.

FIG. 1b is a front view of another stent which is adapted to beconnected to the bifurcated stent of FIG. 1a.

FIG. 2(a) is a side view of part of the bifurcated stent of FIG. 1aopened up to show its construction.

FIG. 2(b) is a side view of an exemplary mandrel used to form the partof the bifurcated stent shown in FIG. 2(a).

FIG. 3 is a side view of another part of the bifurcated stent of FIG. 1aopened up to show its construction.

FIG. 4(a) is a side view of yet another part of the bifurcated stent ofFIG. 1a opened up to show its construction.

FIGS. 4(b)-4(f) are partial exploded views of the exemplary stent ofFIG. 4(a) illustrating alternative means for securing juxtaposed apicesaccording to the present invention.

FIG. 5 is a schematic perspective view of a bifurcated endoluminalprosthesis in accordance with the present invention.

FIG. 6 is a schematic view of another bifurcated endoluminal prosthesisin accordance with the present invention.

FIG. 7 is a schematic view of yet another bifurcated endoluminalprosthesis in accordance with the present invention.

FIG. 8(a) is a cross-sectional view of an exemplary assembled introduceraccording to the present invention.

FIGS. 8(b)-8(e) are side views of the component parts of the introducerof FIG. 8(a).

FIG. 8(f) is a partial cross-sectional view of the introducer of FIG.8(a).

FIG. 8(g) is a cross-sectional view of part of the introducer of FIG.8(f) taken along the line A--A.

FIG. 9 is a side cross-sectional view of a portion an alternativeembodiment of an introducer according to the present invention.

FIGS. 10(a) and 10(b) are side views of other alternative embodiments ofan introducer according to the present invention.

FIGS. 11 through 20 are sequential cross-sectional views of thebifurcation of the abdominal aortic artery during introduction of anexemplary prosthesis according to the present invention.

FIGS. 21(a)-21(c) are cross-sectional views of alternative insertionapparatus according to the present invention.

FIGS. 22 and 23 are side views of alternative stents according to thepresent invention.

FIGS. 24(a), 24(b), 25, 26 and 27 are sequential cross-sectional viewsof the bifurcation of the abdominal aortic artery during introduction ofan exemplary prosthesis according to the present invention.

FIGS. 28 and 29 are cross-sectional side views of alternative deliveryapparatus according to the present invention.

FIGS. 30-34 are sequential cross-sectional views of the bifurcation ofthe abdominal aortic artery during introduction of an exemplaryprosthesis according to the present invention.

DETAILED DESCRIPTION

The present invention includes apparatus and method for treatingangeological diseases in any bifurcated blood vessel. One example ofsuch a bifurcated blood vessel is the infrarenal portion of a mammalianaortic artery where it bifurcates to the common iliac arteries. Examplesof diseases that can be treated using the apparatus and method of thepresent invention include aneurysm, stenosis, and occlusion.

A bifurcated stent in accordance with the present invention which isindicated at 10 in FIG. 1a comprises a wire skeleton which isconstructed in four separate parts, namely a proximal part 12, a firstfrustoconical part 14, a first distal part 16 and a second frustoconicalpart 18. Said bifurcated stent 10 carries a fabric graft layer (FIGS. 5,6, and 7) for use as an endoluminal prosthesis e.g. in the infrarenalportion of a mammalian aorta in juxtaposition with the bifurcation ofthe common iliac arteries. It will be appreciated, however, thatbifurcated stents (with or without fabric graft layers) for use indifferent parts of the angeological system and for different mammals canbe constructed in accordance with the invention by varying thedimensions of the stent accordingly.

Each of the four parts of the bifurcated stent 10 is made insubstantially the same way by winding a shape memory nitinol wire,typically nitinol type M wire, onto a mandrel 46.

The construction of the exemplary proximal part 12 of the bifurcatedstent 10 is shown in FIGS. 2(a) and 2(b); nitinol wire type M wiretypically having a diameter of 0.46 mm (0.018") is wound around mandrel46 to form a plurality of hoops 20. The winding surface of mandrel 46 isprovided with a plurality of upstanding pins 47 disposed in a zig-zagpattern for each of the hoops 20 so that in each hoop 20 the nitinolwire follows a sinuous path to define a plurality of circumferentiallyspaced apices 22. Each hoop 20 is wound onto mandrel 46 such that theplane of the circumference of each hoop 20 is substantiallyperpendicular to the longitudinal axis of the mandrel.

When one hoop 20 e.g. the hoop indicated at 20a has been formed, thepoint of winding of the nitinol wire is displaced longitudinally withrespect to the axis of mandrel 46 to form the next successive hoop 20b.The stent shown in FIG. 2(a) is the stent formed on mandrel 46 shown inFIG. 2(b) after cutting the stent longitudinally and rotating it 45degrees to show the construction of the stent.

The proximal part of the exemplary bifurcated stent of FIG. 1a is formedon the mandrel with a diameter of about 24 mm and a length in thelongitudinal direction of about 55 mm. From FIGS. 1(a), 2(a), and 2(b)it will be noted that the proximal part 12 is constituted by three hoops20 of unit width at the proximal end 24 of the proximal part 12, twointermediate hoops 25 of twice unit width and, at its distal end 26, bya single hoop 20 of unit width. In the illustrated embodiment,intermediate hoops 25 have a plurality of offsets 25a. Offsets 25a areformed when the wire is passed around pins 47 on mandrel 46. Offsets 25aadd stability to the stent. When the nitinol wire has been wound ontomandrel 46, the nitinol wire is annealed at an elevated temperature andthen allowed to cool.

In this embodiment of the invention the wire is annealed at atemperature of about 500° C. for 60 minutes and is then allowed to coolin air. The purpose of the annealing is so that the nitinol wire in itsaustenitic form "remembers" its configuration as wound on mandrel 46; itwill be appreciated therefore that other temperatures and durations forthe annealing are included within the present invention provided thenitinol wire "remembers" its wound configuration.

After annealing and cooling, the wire is immersed in cold water at lessthan 10° C. for about 5 minutes; the wire is then removed from themandrel, and juxtaposed apices 22 of neighboring hoops 20 are securedtogether by securing means 99 (see FIG. 4(a)), which are, in thisexample, 0.003" polypropylene filaments. Each apex 22 of each hoop 20which has a juxtaposed apex of a neighboring hoop 20 is tied to thejuxtaposed apex 22. It will be appreciated, however, that in otherembodiments of the invention only some of the juxtaposed apices 22 maybe secured in this way.

In addition to polypropylene filaments, the securing means may comprisea loop element 99a of a suture material, for example, to tie thejuxtaposed apices together, as shown in FIG. 4(b). The securing meansmay also comprise bead 99b formed of a thermoplastic material aroundjuxtaposed apices, as shown in FIG. 4(c). Also alternatively, thesecuring means may be a loop 99c, ring 99d, or staple 99e formed of wiresuch as nitinol, as shown in FIGS. 4(d), 4(e), and 4(f) respectively.

The exemplary first and second frustoconical parts 14, 18 of theskeleton shown in the figures are formed in substantially the same wayas the proximal part 12 by winding nitinol wire onto a mandrel and thenannealing the wire before removing it from the mandrel. As shown in FIG.3, the first and second frustoconical parts 14, 18 are each constitutedby three hoops 20 of unit width. The mandrel is tapered such that theproximal end of each of the exemplary frustoconical parts 14, 18 isformed with a diameter of about 12 mm and the distal end 32 of each isformed with a diameter of about 9 mm. The overall length of each of theexemplary frustoconical parts 14, 18 is about 18 mm. The wire used forthe frustoconical parts 14, 18 is nitinol type M wire having a diameterof 0.28 mm (0.011"). Juxtaposed apices 22 of each of the exemplaryfrustoconical parts 14, 18 are tied together using 0.03" polypropylenefilaments as described above. The first and second frustoconical parts14, 18 are secured to the distal end 26 of the proximal part 12 of thestent 10 in transversely spaced relation as shown in FIG. 1a by securingthe apices 22 of the hoop 20 forming the wider proximal end 30 of eachof the frustoconical parts 14, 18 to juxtaposed apices 22 of the hoop 20on the distal end 26 of the proximal part 12.

The exemplary first distal part 16 of the bifurcated stent 10 is formedby winding nitinol type M wire typically having a diameter of 0.28 mm(0.011") onto a mandrel to form twelve longitudinally spaced hoops 20 asshown in FIG. 4; the exemplary first distal part has an overall lengthof about 66 mm and a uniform diameter of about 9 mm. The proximal end 34of the distal part 16 is secured to the narrower distal end 32 of thefirst frustoconical part 14 by tying each apex 22 on the proximal end 34of the first distal part 16 to a juxtaposed apex on the distal end 32 ofthe first frustoconical part 14 using, in this embodiment, 0.003"polypropylene filaments.

The proximal part 12, the first and second frustoconical parts 14, 18,and the first distal part 16 are each covered with a tubular graft layerof a biocompatible woven fabric (FIGS. 5, 6, and 7) such, for example,as a plain woven fabric made from 30 or 40 denier polyester. The tubularfabric layers may be attached to the proximal and distal parts 12, 16 ofthe stent 10 by stitching with, for example, 0.003" polypropylenefilaments around the apices 22 of the underlying skeleton. The fabriccovered stent constitutes one form of an endoluminal prosthesis.

The proximal part 12 of the wire skeleton may be provided with aplurality of circumferentially spaced hooks or barbs 43 which projectthrough the tubular fabric layer to engage in the endoluminal surface ofa host artery in service.

The sinuous configuration of each turn 20 of the wire skeleton of thestent 10 allows the prosthesis to be compressed resiliently radiallyinwards so that it can be received in a catheter e.g. a 16 or 18 Frenchcatheter for percutaneous or cut down delivery, e.g. to an intraluminalsite in the infrarenal section of the aortic artery. Larger diametercatheters up to, e.g., 20 French, may be used to deliver the prosthesisusing "cut down" procedures.

An x-ray opaque marker may be attached to one or more ends of a stent sothat the delivery of the stent can be monitored using x-rays. As shownin FIG. 4(a), such a radiopaque marker may typically comprise a gold orplatinum wire 17 crimped onto an end of stent 16. Alternatively, theradiopaque marker may be a tube 17a disposed around a length of wire onthe stent, also as shown in FIG. 4(a). Typically, in the bifurcatedstent the marker is secured to the stent in line with the distal stentportion so that the distal stent portion can be aligned with andinserted into one of the branched arteries in situ.

The bifurcated endoprosthesis is positioned in the infrarenal section ofthe aortic artery in juxtaposition with the bifurcation of the commoniliac arteries such that the first distal part 16 of the prosthesisextends into one of the common iliac arteries. The catheter is thenwithdrawn allowing the stent 10 to re-expand towards its configurationas wound on the mandrel in which it was annealed until the stent engagesthe endoluminal surface of the host artery. The barbs or hooks engagethe endoluminal surface of the host artery to resist longitudinaldisplacement or slipping of the prosthesis in use.

It will be appreciated that when the bifurcated prosthesis is positionedand re-expanded in the fitted position, blood can flow from the aorticartery into the proximal part 12 of the prosthesis from where it canflow into the one common iliac artery through the frustoconical part 14and the first distal part 16 and also into the other common iliac arterythrough the second frustoconical part 18.

In cases where it is required to implant a prosthesis in the othercommon iliac artery a second prosthesis comprising a second stent 40 asshown in FIG. 1b can be used. The second stent 40 includes a wireskeleton comprising a proximal frustoconical part 42 and a distal part44. The distal part 44 of the second stent 40 also may be covered with atubular graft layer of a biocompatible fabric such, for example, aspolyester or polytetrafluoroethylene fabric (FIGS. 5, 6, and 7).

The frustoconical proximal part 42 is constructed in the same way as thefrustoconical parts 14, 18 of the bifurcated stent 10; the distal part44 is constructed in the same way as the distal part 16 of thebifurcated stent 10. The distal end of the frustoconical proximal part42 is secured to the proximal end of the distal part 44 by securingjuxtaposed apices using polypropylene filaments as described above.

In use, the second prosthesis is compressed radially inwards and isreceived in a catheter for percutaneous or "cut down" delivery to theother common iliac artery. The frustoconical proximal part 42 is guided,in the radially compressed state, into the second frustoconical part 18of the bifurcated stent 10. The catheter is then withdrawn allowing thesecond stent 40 to re-expand towards its remembered configuration, untilthe distal part 14 engages the endoluminal surface of the other commoniliac artery, and the outer surface of the frustoconical proximal part42 engages the interior surface of the second frustoconical part 18 ofthe bifurcated stent 10.

As with other stents described herein, the frustoconical proximal part42 may be formed with circumferentially spaced barbs or hooks 43, asshown in FIG. 1b, which engage in the wire skeleton of the secondfrustoconical part 18 of the bifurcated stent 10. When barbs 43 are onproximal portion 12, they engage the inner wall of the artery.

The tapered configurations of the second frustoconical part 18 of thebifurcated stent 10 and of the proximal frustoconical part 42 of thesecond stent 40 are such that in the fitted position as described, theprosthesis are locked together to resist longitudinal separation inservice. Barbs or hooks on the second stent 40 and/or an frustoconicalproximal part 42 help to resist such longitudinal separation.

In another example of the present invention a bifurcated endoluminalprosthesis 50 as shown in FIG. 5 includes a bifurcated stent comprisinga proximal portion 52 which tapers radially inwardly from its proximalend 54 to its distal end 56, and first and second transversely spacedfrustoconical distal portions 58, 60 which are secured to the distal end56 of the proximal portion 52; the proximal portion 52 is covered with atubular graft layer of a biocompatible fabric 62.

In use the prosthesis is delivered percutaneously or by "cut down"methods to an artery in juxtaposition with an arterial bifurcation;blood can flow through the frustoconical proximal portion 52 into eachof the branched arteries through the first and second distalfrustoconical portions 58, 60. If a prosthesis is required in one orboth of the branched arteries, a separate prosthesis comprising a stentof the type shown in FIG. 1b referred to above covered with fabric canbe connected to the bifurcated prosthesis 50 by inserting andre-expanding the proximal end of such a separate prosthesis in one orboth of the distal frustoconical portions 58, 60 of the prosthesis 50for engagement therein.

Another variant of the present invention is shown in FIG. 6 which showsa bifurcated endoluminal prosthesis 70 having a proximal portion 72which is secured at its distal end 74 to two transversely spacedfrustoconical intermediate portions 76, 78.

One of said frustoconical intermediate portions 76 is secured at itsdistal end to an elongate distal portion 80. The proximal end 82 of theproximal portion 72 is flared radially outwards towards its proximal end82 to engage the intraluminal surface of the host blood vessel inservice. Save for this flared portion, the entire endoprosthesis iscovered with a fabric graft layer as shown in FIG. 6; said graft layeris carried externally of the wire skeleton and is folded over the distalextremity 84 of the other frustoconical intermediate portion 78 to forman internal lining in said other frustoconical immediate portion 78.

Said other frustoconical intermediate portion 78 constitutes a femalecooperating portion in accordance with the present invention which isadapted to receive a male engaging portion of another prosthesis asindicated at 86 in FIG. 6. Said other prosthesis 86 includes afrustoconical proximal portion 88 which constitutes the male engagingportion and an elongate distal portion 90. The whole of the otherprosthesis 86 is covered with a fabric graft layer as shown in FIG. 6.In service, the male engaging portion 88 of the other prosthesis 86 isentered into and engaged with the female cooperating portion 78 of thebifurcated prosthesis 70 in situ in the manner herein before described.The fabric layer on the male engaging portion 88 butts face-to-face onthe folded over portion of the fabric layer disposed internally of thefemale cooperating portion 78 to form a substantially blood-tight sealtherewith.

Yet another example of the present invention is shown in FIG. 7 in whicha bifurcated endoluminal prosthesis 91 has a generally cylindricalproximal portion 92; said proximal portion 92 is connected at its distalend 93 to an elongate, generally cylindrical distal portion 94. Saidproximal portion 92 is also connected at its distal end 93 to agenerally cylindrical intermediate portion 95 which is secured intransversely spaced relation to the elongate distal portion 94. Saidcylindrical intermediate portion 95 constitutes a female engagingportion which is adapted to receive a generally cylindrical maleengaging portion of a second elongate prosthesis (not shown). The maleengaging portion is equipped with circumferentially spaced externalbarbs to engage in the female cooperating portion in service. As shownin FIG. 7, the whole of the bifurcated prosthesis 91 is covered with anexternal fabric graft layer save for a flared portion 96 towards theproximal end 97 of the proximal portion 92.

Referring to FIGS. 8(a)-8(f), an exemplary embodiment of a deliverysystem according to the present invention will be described. This systemis used to deploy the bifurcated stent 10 when it is covered with afabric graft layer to create an endoluminal prosthesis. Introducer 100includes outer sheath 101. Outer sheath 101 is a cylindrical tubeadapted to be inserted either percutaneously or by "cut-down" proceduresinto the vasculature from an entry point to the bifurcation site wherethe prosthesis is to be deployed.

Housed within outer sheath 101 is proximal portion pusher 102. Proximalportion pusher 102 is a cylindrical tube having an outside diametersmaller than the inside diameter of outer sheath 101. Proximal portionpusher 102 is preferably slidable throughout the length of outer sheath101.

Disposed within proximal portion pusher 102 is distal portion pusher103. Distal portion pusher 103 is a cylindrical tube slidably containedwithin distal portion pusher 102. Distal portion pusher 103 ispreferably adapted to slide throughout the entire length of proximalportion pusher 102.

Disposed within distal portion 103 is balloon catheter 104. Ballooncatheter 104 is adapted to slide within distal portion pusher 103. Atthe leading end 105 of balloon catheter 104 is nose cone 106. Balloon107 is attached to balloon catheter 104 between nose cone 106 andproximal end 115 of proximal portion pusher 102.

As shown in FIG. 8(g), which is a cross-sectional view of ballooncatheter 104 in the direction A--A of FIG. 8(f), balloon catheter 104has a guide wire conduit 104a. Guide wire conduit 104a extendsthroughout the length of balloon catheter 104 for passing a guide wire(not shown) through introducer 100. In the illustrated embodiment,balloon catheter 104 also includes injection orifice 109 and aninjection conduit 109a. Injection conduit 109a connects injectionorifice 109 to an injection site 108 at or near the distal end ofballoon catheter 104 as shown in FIG. 8(e). Radiopaque liquid may beinjected into injection site 108, through injection conduit 109a, outinjection orifice 109, and into the vasculature to monitor deployment ofthe prosthesis.

Also in the illustrated embodiment of FIGS. 8(f) and 8(g), ballooncatheter 104 has an inflation orifice 110 located at a point whereballoon 107 is attached to balloon catheter 104. A balloon inflationconduit 110a connects balloon inflation orifice 110 to balloon inflationsite 111 (FIG. 8(e)). Balloon 107 may be inflated and deflated fromballoon inflation site 111 during delivery of the prosthesis.

In an alternative embodiment illustrated in FIG. 9, seals 150, 151 maybe disposed around the distal ends 160, 161 of outer sheath 10 andproximal portion pusher 102. Seals 150, 151 may be formed of siliconetubes.

FIG. 10(a) shows an alternative embodiment of introducer 100. As shownin FIG. 10(a), wings 112 and 113 are provided at the distal end ofintroducer 100. Wing 112 is connected to proximal portion pusher 102,and wing 113 is connected to outer sheath 101. Wings 112 and 113indicate the rotational orientation of proximal portion pusher 102 andouter sheath 101, respectively. This in turn indicates the orientationof proximal portion 12 within outer sheath 101 and distal portion 16within proximal portion pusher 102. Wings 112 and 113 in the illustratedembodiment are also provided with holes 112a and 113a.

As shown in FIG. 10(b), a rod 128 or other fixation device may beattached to wings 112 and 113 using e.g. bolts through holes 112a and113a secured by wing nuts 129 or other securing means. Rod 128 preventsrelative movement of proximal portion pusher 102 and outer sheath 101.Wings may also be provided on distal portion pusher 103 and used tosecure distal portion pusher 103 to either proximal portion pusher 102or outer sheath 101 using a fixation device as described above.

Also shown in FIG. 10(a) as part of introducer 100 is hemostasis valve114. Hemostasis valve 114 is connected to distal portion pusher 103 andacts as a simple seal around balloon catheter 104. Although it preventsfluid loss, hemostasis valve 114 allows balloon catheter 104 to slidewithin distal portion pusher 103. Alternatively, a Touhy-Borst valve(not shown) may be used instead of hemostasis valve 114. The Touhy-Borstvalve is a device that may be manually tightened over balloon catheter104. Lightly tightening such a valve permits balloon catheter 104 toslide; firmly tightening such a valve clamps balloon catheter 104 inplace.

In use, the prosthesis must first be loaded into introducer 100. Outersheath 101 is first removed from introducer 100. Balloon catheter 104 isthen threaded through distal portion 16 and proximal portion 12 of theprosthesis. The prosthesis is then cooled to a temperature ofapproximately 10° C. or below and radially compressed. For this purpose,the prosthesis may be immersed in cold water. The prosthesis shouldpreferrably remain in the water during the loading operation.

As supporting stent 10 is compressed beneath the fabric covering of theprosthesis, excess fabric is produced. This excess fabric may simply bepinched together and laid over the compressed prosthesis in longitudinalfolds.

Distal portion 16 of the prosthesis in the radially compressed state isthen inserted into proximal portion pusher 102. Outer sheath 101 is thenpulled over proximal portion 12 of the prosthesis and over proximalportion pusher 102. A thread (not shown) may be attached to the proximalend of proximal portion 12 of the prosthesis and threaded through outersheath 101. This thread may then be used to pull proximal portion 12through outer sheath 101. During the loading process, it is important tokeep proximal portion 12 and distal portion 16 of the prosthesisproperly aligned with outer sheath 101 and proximal portion pusher 102.Marks may be placed on the outside of outer sheath 101 and proximalportion pusher 102 to ensure proper alignment.

Referring again to FIG. 8(f), the prosthesis is inserted such that theouter surface of proximal portion 12 contacts and is radially restrainedby outer sheath 101, and the outer surface of distal portion 16 contactsand is radially restrained by proximal portion pusher 102. End 115 ofproximal portion pusher 102 longitudinally engages proximal portion 12of the prosthesis as shown in FIG. 8(f).

Balloon catheter 104 is positioned such that nose cone 106 just clearsproximal end 117 of outer sheath 101. The introducer is now in conditionfor insertion into the patient.

Referring to FIG. 11, introducer 100 is passed through an entry point(not shown) either in the patient's skin (percutaneous operation) orinto the vasculature itself which has been surgically exposed("cut-down" operation). Introducer 100 is inserted over a guide wire 170into the vasculature from the entry point to the desired deliverylocation at an angeological bifurcation.

In the aorta, introducer 100 is positioned such that end 117 of outersheath 101 is approximately level with renal arteries 180 as shown inFIG. 11. Balloon catheter 104 is then extended while maintaining outersheath 101 in a fixed position. Balloon catheter 104 in this embodimentis extended until distal end 105 of nose cone 106 is approximately 35 mmabove the proximal tip 117 of outer sheath 101. Then, while maintainingproximal portion pusher 102 in a fixed position, outer sheath 101 iswithdrawn until the proximal tip of the prosthesis is level withproximal tip 117 of outer sheath 101. It will be noted that ballooncatheter 104 does not move while outer sheath 101 is so withdrawn.

Introducer 100 is then repositioned to place the prosthesis in thedesired deployment location. Proper placement may be facilitated withthe use of radiopaque markers as described above. Balloon catheter 104is then extended such that balloon 107 is above renal arteries 180.Balloon 107 is then inflated to occlude the aorta as shown in FIG. 12.

While maintaining proximal portion pusher 102 in a fixed position, outersheath 101 is withdrawn until the proximal end of the prosthesis emergesfrom outer sheath 101 as shown in FIG. 13. Using a radiopaque marker 120disposed on proximal end of the prosthesis, the introducer is rotateduntil proper alignment of the prosthesis is obtained. In the illustratedembodiment, radiopaque marker 120 is a platinum wire twisted around anapex of the prosthesis in a "V" shape. To ensure proper alignment, thestent should be rotated until only the profile of the V is seen andshows up as a straight line rather than a "V".

Outer sheath 101 is further withdrawn while maintaining proximal portionpusher 102 fixed until proximal portion 12 is fully deployed from theend of outer sheath 101, and the frustoconical portion 18 of theprosthesis just clears end 117, as shown in FIG. 14.

Balloon 107 is then deflated to allow blood to flow through proximalportion 12 and out frustoconical portion 18 of the prosthesis. Balloon107 is withdrawn into the prosthesis until the distal end 118 of nosecone 106 is just above the proximal end of the prosthesis. Balloon 107is then inflated to seat the prosthesis, which may be provided withbarbs (not shown) at its proximal end, against the wall of the aorta, asshown in FIG. 15.

Distal portion pusher 103 is then maintained in a fixed position whileouter sheath 101 is withdrawn. Once outer sheath 101 has been withdrawnto the point at which proximal end 117 of outer sheath 101 is flush withproximal end 115 of proximal portion pusher 102, both outer sheath 101and proximal portion pusher 102 are withdrawn, still maintaining distalportion pusher 103 in a fixed position. Outer sheath 101 and proximalportion pusher 102 are withdrawn until distal portion 16 of theprosthesis is deployed clear of proximal end 116 of distal portionpusher 103 as shown in FIG. 16. Balloon 107 is slowly deflated to allowblood flow to be established through the proximal portion 12 of theprosthesis and out through frustoconical portion 18. Balloon 107 may beused to model distal portion 16 of the prosthesis as necessary byinflating balloon 107 where needed to expand distal portion 16. Balloon107 is then deflated, and introducer 100 is withdrawn from thevasculature, leaving the guide wire 170 in place, as shown in FIG. 17.

FIG. 21(a) illustrates an exemplary second introducer 300 used fordeploying second distal part 44 (as shown FIG. 21(b)). Second introducer300 of the illustrated embodiment comprises cylindrical outer sheath 301and female Luer lock assembly 310. Second introducer 300 also hashemostasis valve 361 contained within a hub 362 thereof. Cartridge 311shown in FIG. 21(b) is adapted to be attached to second introducer 300.Cartridge 311 has threaded male Luer lock assembly 312 provided on itsproximal end. Cartridge 311 has outer tube 313 which houses inner tube314.

In use, a thin-walled tube (not shown) is first threaded through distalportion 44. This tube serves as a guide wire guide, allowing a guidewire to be threaded straight through distal portion 44 as discussedbelow. Distal portion 44 containing the thin-walled tube is then cooled,radially compressed, and inserted into inner tube 314 of cartridge 311in a manner similar to that described for inserting the bifurcatedprosthesis into proximal portion pusher 102 and outer sheath 101. Whendistal portion 44 has been loaded into inner tube 314 of cartridge 311,the thin-walled tube serving as a guide wire guide extends out both endsof cartridge 311.

A guide wire 171 is then inserted into the vasculature to thebifurcation site and through distal stent portion 12 as shown in FIG.18. A dialator 359 (FIG. 21(c)) having an outer diameter slightly lessthan the inner diameter of second introducer 300 is then inserted intosecond introducer 300 such that tapered end 360 extends out end 320 ofsecond introducer 300. End 360 of dialator 359 has a hole therein thatis just slightly larger than guide wire 171 and tapers gradually outwardfrom the hole to the outer diameter of dialator 359.

Second introducer 300 is then inserted into the vasculature over guidewire 171 by passing guide wire 171 into and through dialator 359.Dialator 359 with tapered end 360 provides a smooth transition withinthe blood vessel from the diameter of guide wire 171 to the diameter ofsecond introducer 300. Second introducer 300 is maneuvered such thatouter sheath 301 is inside frustoconical portion 18 of proximal portion12 by at least 20 mm in this embodiment, as shown in FIG. 19. Dialator359 is then removed from second introducer 300 and from the vasculatureand is discarded.

Cartridge 311 is then passed over guide wire 171 by passing guide wire171 through the thin-walled guide wire guide within distal portion 44contained in cartridge 311. The guide wire guide is then removed anddiscarded.

Cartridge 311 is then lockingly engaged with introducer 300 by matingmale Luer lock assembly 310 with female Luer lock assembly 312. Suchlocking engagement prevents relative movement of cartridge 311 andintroducer 300. Preventing relative movement lends stability andreliability to the insertion process that has not heretofore beenachieved.

A pusher 315 is then inserted into inner tube 314 of cartridge 311 suchthat proximal end 317 of pusher 315 longitudinally contacts a distal endof distal portion 44 within inner tube 314. Pusher 315 pushes distalportion 44 through cartridge 311 and into outer sheath 301 of introducer300. Distal portion 44 is pushed through outer sheath 301, which remainsin a fixed position, until distal portion 44 is at proximal end 320 ofouter sheath 301 (see FIG. 19). Again, radiopaque markers 120 may beused to align distal portion 44 properly with proximal portion 12.

Pusher 302 is held firmly in place, and outer sheath 301 is withdrawnapproximately 2 cm. This deploys frustoconical part 42 of distal part 44inside the frustoconical part 18 as shown in FIG. 19. The outer surfaceof frustoconical part 42 engages the inner surface of frustoconical part18 such that distal portion 44 is connected to proximal portion 12 toresist longitudinal separation.

Outer sheath 301 may then be withdrawn while maintaining pusher 302 in afixed position to fully deploy distal portion 44, as shown in FIG. 20.If necessary, balloon catheter 104 may be inserted through sheath 301 inorder to model distal portion 44. Introducer 301 and guide wires 170,171 are then removed from the vasculature and the entry points areclosed.

The delivery apparatus and method described above are particularlyuseful in treating an abdominal aortic aneurysm with a bifurcatedprosthesis according to the present invention. Other diseases andalternative embodiments of the prosthesis and delivery method will nowbe described.

In the case of an abdominal aortic aneurysm confined to the aorta andnot extending far enough to affect the iliac arteries, a straight (i.e.non-bifurcated) stent may be used. Preferably, for such applications,the straight stent comprises a composite of at least two axially alignedstent segments. Two embodiments of such straight stents are describedherein, each comprising axially aligned stent requests, each of therequests comprising one or more adjacent hoops, perpendicular to acommon axis, and each hoop being formed of wire in a sinuous or zigzagconfiguration with some or all of the juxtaposed apices in adjacenthoops secured to one another.

First, referring to FIG. 22, straight stent 400 comprises proximal stentportion (or segment) 401, distal stent portion 402, and an intermediateportion 403.

Proximal portion 401 is a ring formed of a number of longitudinallyspaced hoops 20 as described in connection with the formation of stent10 above. In the illustrated embodiment, two hoops 20 are used, eachhoop 20 having a unit width.

Distal portion 402 is also a ring formed of longitudinally displacedhoops 20 in the manner described above. Distal ring 402 has two hoops 20of unit width in the illustrated embodiment.

Intermediate portion 403 of straight stent 400 is formed ofbiocompatible woven fabric such as, for example, a plain woven fabricmade from 30 or 40 denier polyester. In this embodiment, intermediatefabric section 403 does not cover a stent. Fabric portion 403 isattached at its proximal and distal ends to the proximal and distalstent portions, respectively, by stitching, for example, with 0.003 inchpolypropylene filaments around apices 22 of the stent portions. Otherthan such connections at its longitudinal ends, intermediate fabricsection 403 is unsupported by any stent.

The second embodiment of a straight stent that may be used according tothis invention is illustrated in FIG. 23. Straight stent 450 includesstent portion 451, constructed of wire loops as described above withreference to stent portions 401 and 402. Stent portion 451 is partiallycovered by fabric 452. In this embodiment, fabric portion 452 covers andis supported by stent 451, whereas with stent 400, the fabric portion403 is not supported by a stent.

To treat an abdominal aortic aneurysm that does not extend down over thewalls of the lilac arteries, as shown in FIG. 24(a), straight stent 400(or 450) is disposed as illustrated in FIG. 26. Proximal stent portion401 engages the inner walls of the aorta above the aneurysm. Distalstent portion 402 engages the inner wall of the aorta below theaneurysm. Intermediate fabric portion 403 extends across the aneurysm,providing a strong, stable lumen for blood flow through the aorta.

FIG. 28 illustrates the delivery apparatus used to implant straightstent 400 in the vasculature. This apparatus is very similar to thatdescribed above for the delivery system to be used with the bifurcatedstent or prosthesis. Accordingly, like reference numerals refer to thesame components.

In the introducer 410 shown in FIG. 28, proximal portion pusher 102engages proximal stent portion 401. Distal portion pusher 103 engagesdistal stent portion 402.

In use, straight stent 400 is first charged into the introducer bycooling it to temperatures below 10° C., radially compressing it, andinserting it within outer sheath 101, as described above in connectionwith the bifurcated stent or prosthesis. The remainder of introducer 410is also assembled as described in connection with introducer 100.

Introducer 410 is passed through an entry point (not shown) over guidewire 411 as shown in FIG. 24(a). This insertion may be accomplishedusing percutaneous or cut-down techniques. Introducer 410 is theninserted to the desired delivery location.

In the aorta, introducer 410 is positioned and balloon 107 is inflatedabove the renal arteries in the same manner as described above inconnection with the bifurcated stent and as illustrated in FIG. 24(a).

While maintaining proximal portion pusher 102 in a fixed position, outersheath 101 is withdrawn until proximal portion 401 of stent 400 emergesfrom outer sheath 101 as shown in FIG. 24(b). Using a radiopaque marker420 disposed on the proximal end of the proximal portion 401, stent 400is optimally aligned within the aorta. Outer sheath 101 is furtherwithdrawn until proximal portion 401 emerges therefrom, as shown in FIG.25. Outer sheath 101 is then further withdrawn until it is flush withproximal portion pusher 102. Then both outer sheath 101 and proximalportion pusher 102 are withdrawn while maintaining distal portion pusher103 in a fixed position. Distal portion 402 is thus deployed from theend of outer sheath 101, as shown in FIG. 26.

Balloon 107 is then deflated and withdrawn inside proximal portion 401where balloon 107 is reinflated to seat the stent 400, as shown in FIG.27. Balloon 107 is then withdrawn, along with the introducer 410 asdescribed above, and the entry point is closed.

FIG. 29 illustrates the apparatus used to deploy straight stent 450,shown in FIG. 23, of the present invention. This apparatus is verysimilar to that described above for the delivery system to be used withthe bifurcated stent or prosthesis. Accordingly, like reference numeralsrefer to the same components.

Proximal portion pusher 102 in this embodiment is glued to distalportion pusher 103 such that ends 115 and 116 are flush. These flushends are adapted to engage stent 450 within outer sheath 101.

In use, straight stent 450 is first charged into introducer 490 bycooling it to temperatures below 10° C., radially compressing it, andinserting it within outer sheath 101, as described above in connectionwith the bifurcated stent or prosthesis. The remainder of introducer 490is also assembled as described in connection with introducer 100.

Introducer 490 is passed through an entry point (not shown) over a guidewire 411 as shown in FIG. 30. This insertion may be accomplished usingpercutaneous or cut-down techniques. Introducer 490 is then inserted tothe desired delivery location.

In the aorta, introducer 490 is positioned and balloon 107 is inflatedabove the renal arteries in the same manner as described above inconnection with the bifurcated stent and as illustrated in FIG. 31.

While maintaining attached proximal portion pusher 102 and distalportion pusher 103 in a fixed position, outer sheath 101 is withdrawnuntil proximal portion 451 of stent 450 emerges from outer sheath 101 asshown in FIG. 32. Using a radiopaque marker 420 disposed on the proximalend of the proximal portion 451, stent 450 is optimally aligned withinthe aorta. Outer sheath 101 is then completely withdrawn until stent 450is deployed into the aorta as shown in FIG. 33.

Balloon 107 is then deflated and withdrawn inside proximal portion 451where balloon 107 is reinflated to seat the stent 450, as shown in FIG.34. Balloon 107 is then withdrawn, along with the introducer 490 asdescribed above, and the entry point is closed.

The angeological disease of occlusion is the blockage of an arteryresulting from a buildup or clot of soft thrombus. There are two typesof occlusions that can occur at the aorta-iliac bifurcation. The firstis infrarenal occlusion. In this case, the blockage extends in the aortafrom just below the renal arteries into the iliac arteries. The secondtype is an occlusion that is limited to the immediate area of thebifurcation.

To treat an infrarenal occlusion, a canalization is first made throughthe thrombus by methods known in the art. A bifurcated endoluminalprosthesis according to the present invention is then implanted at thebifurcation site to provide an unobstructed lumen extending from theaorta into each of the iliac arteries. Blood can thus flow freely fromthe aorta to the iliac arteries.

The bifurcated endoluminal prosthesis according to the present inventionthat is used to treat an occlusion must be fabric covered. This isnecessary to prevent embolization from the thrombus remaining on thewall of the recanalized artery.

An occlusion at the bifurcation is treated by recanalizing the artery asabove. A bifurcated endoluminal prosthesis according to the presentinvention may be implanted at the bifurcation. Because the occlusion islimited to the immediate bifurcation site, however, the proximal portionof the prosthesis may be shorter than that discussed above.

To implant the bifurcated endoluminal prosthesis to treat both types ofocclusion, the delivery system comprising introducer 100 discussed abovefor delivering the bifurcated endoluminal prosthesis to treat anabdominal aortic aneurysm is used. The same delivery method discussedabove for implanting the bifurcated endoluminal prosthesis to treatabdominal aortic aneurysms is used to implant the device to treat theocclusion.

Using the method and apparatus of this invention to treat occlusionprovides an unobstructed lumen through which blood can flow from theaorta to the iliac arteries.

The angeological disease of stenosis is a narrowing of an artery causedby a buildup of hard calcified plaque. This is usually caused by abuildup of cholesterol. To treat such an angeological disease,angioplasty is performed on the plaque according to methods well knownin the art. The bifurcated endoluminal stent according to the presentinvention is then implanted at the bifurcation site. This stent is thesame as that described above for treatment of an abdominal aorticaneurysm. To treat the stenosis, however, it is not necessary to coverthe stent with a fabric, thus creating a prosthesis. Because restenosisis rare at the bifurcation site, there is no need to isolate the bloodflowing in the lumen from the walls of the arteries.

The delivery system used to implant the bifurcated endoluminal stentused to treat stenosis is the same as that illustrated in FIG. 8 exceptthat balloon 107 is not required. Because there is no fabric around thestent to be affected by blood flow in the arteries and cause migrationof the bifurcated stent, it is not necessary to block the blood flowwith the balloon. Otherwise, the delivery system for implanting thebifurcated stent to treat stenosis is the same as that for implantingthe bifurcated prosthesis to treat abdominal aortic aneurysm.

Similarly, with the exception of the steps involving inflation ofballoon 107 to block blood flow, the method of delivering the bifurcatedendoluminal stent to treat stenosis is the same as that described abovefor delivering the bifurcated endoluminal prosthesis to treat abdominalaortic aneurysm.

What is claimed:
 1. A stent joining means for joining a firstendoluminal stent to a second endoluminal stent to define a continuouslumen through the first and second endoluminal stents, said stentjoining means comprising:a male engaging portion on said firstendoluminal stent which has an outer surface and can be compressedradially inwardly; and a female portion on said second endoluminal stentcooperating with said male engaging portion, said female portion havingan inner surface; wherein said first endoluminal stent and said secondendoluminal stent consist of a shape memory alloy and the male engagingportion can be entered into the female portion in a radially compressedstate and thereafter thermally induced to expand in the female portionand wherein a frictional inter-engagement between said outer surface ofthe male engaging portion and said inner surface of the female portionprevents longitudinal movement of the first endoluminal stent relativeto the second endoluminal stent.
 2. A stent joining means as claimed inclaim 1 wherein a proximal end of said second endoluminal stent isflared radially outwardly towards a proximal end extremity; saidextremity thereby being adapted to engage an endoluminal surface of theblood vessel thereby to resist longitudinal movement of the secondendoluminal stent.
 3. A stent joining means as claimed in claim 1wherein each of said first and second endoluminal stents comprises asinuous wire formed into a tubular configuration.
 4. A stent joiningmeans as claimed in claim 1 wherein each of said first and secondendoluminal stents is formed from a shape memory nitinol wire.
 5. Astent joining means as claimed in claim 1 wherein said secondendoluminal stent is adapted to extend across a bifurcation in a bloodvessel such that in use a proximal end of the second endoluminal stentis disposed proximally of the bifurcation, and a distal end of thesecond endoluminal stent is disposed in one of the branched bloodvessels; said female portion is disposed intermediate said proximal anddistal ends; and said first endoluminal stent is adapted to extend inthe other branched blood vessel.
 6. A stent joining means as claimed inclaim 1 wherein at least one of said first endoluminal stent and saidsecond endoluminal stent includes a portion having a graft layerdisposed internally and externally of said stent.
 7. A stent joiningmeans as claimed in claim 1 wherein the male engaging portion is at aproximal end of said first stent.
 8. A stent joining means as claimed inclaim 1 wherein the female portion is at a distal end of said secondstent.
 9. A stent joining means as claimed in claim 1 wherein said maleengaging portion is flared radially outwardly towards a proximal end.10. A stent joining means as claimed in claim 1 wherein the femaleportion is tapered radially inwardly towards a distal end.
 11. A stentjoining means as claimed in claim 1 wherein the male engaging portioncomprises a frustoconical wall flaring outwardly towards a longitudinalextremity.
 12. A stent joining means as claimed in claim 1 wherein thefemale portion comprises a frustoconical wall tapering radially inwardlytowards a longitudinal extremity.
 13. A stent joining means as claimedin claim 1 wherein said male engaging portion and said female portionare substantially untapered.
 14. A stent joining means as claimed inclaim 1 wherein said male engaging portion and said female portion aresubstantially cylindrical.
 15. A stent joining means as claimed in claim1 wherein said male engaging portion is resiliently compressible in aradially inwards direction such that in a radially compressed state themale engaging portion is capable of self re-expansion to engage thefemale portion.
 16. A stent joining means as claimed in claim 1 whereineach of said first and second endoluminal stents is compressible andexpandable.
 17. A stent joining means as claimed in claim 1 wherein saidsecond endoluminal stent has two transversely spaced distal femaleportions.
 18. A stent joining means as claimed in claim 17 wherein oneof said two transversely spaced distal female portions is adapted forconnection to said male engaging portion of said first endoluminal stentand said one spaced distal female portion and said first and secondendoluminal stents, in combination, extend across a bifurcation in ablood vessel into two respective branched blood vessels.
 19. A method ofjoining a first endoluminal stent having an outer surface with a secondendoluminal stent having an inner surface within the vasculature of abody comprising the steps of inserting an end of said first endoluminalstent at least partially into an end of said second endoluminal stent,and allowing said end of said first endoluminal stent to expand bythermal transformation and contact said end of said second endoluminalstent such that said outer surface of said first endoluminal stentfrictionally engages said inner surface of said second endoluminal stentto prevent relative longitudinal movement of said first and secondendoluminal stents.
 20. A method of forming an endoluminal stent withinthe vasculature of a body comprising inserting an end of a first stentportion having an outer surface at least partially into an end of asecond stent portion having an inner surface, and allowing said end ofsaid first stent portion to expand by thermal transformation and contactsaid end of said second stent portion such that said outer surface ofsaid first stent frictionally engages said inner surface of said secondstent to prevent relative longitudinal movement of said first and secondstents.
 21. A method as claimed in claim 20 wherein a tubular graftlayer comprised of a bio-compatible fabric is disposed in juxtapositionwith each of said first stent portion and said second stent portion. 22.A stent joining means for joining a first endoluminal stent to a secondendoluminal stent comprising:a male engaging portion on said firstendoluminal stent, having a first graft layer disposed externally ofsaid male engaging portion, wherein the male engaging portion can becompressed radially inwardly; and a female portion on said secondendoluminal stent cooperating with said male engaging portion and havinga second graft layer disposed internally of said female portion; whereinthe male engaging portion can be entered into the female portion in aradially compressed state and thereafter caused or allowed to expand inthe female portion and wherein a frictional inter-engagement of thefirst graft layer of the male engaging portion and the second graftlayer of the female portion prevents relative movement of the firstendoluminal stent and the second endoluminal stent.
 23. A stent joiningmeans for joining a first endoluminal stent having a male portion end toa second endoluminal stent having a female portion end comprising:a maleengaging portion on said male portion end of said first endoluminalstent, defining a first frustoconical wall which is flared radiallyoutwardly towards said male portion end, and which can be compressedradially inwardly; and a female portion on said female portion end ofsaid second endoluminal stent cooperating with said male engagingportion and defining a second frustoconical wall which is taperedradially inwardly towards said female portion end; wherein the maleengaging portion can be entered into the female portion in a radiallycompressed state and thereafter caused or allowed to expand in thefemale portion and wherein a frictional inter-engagement of the maleengaging portion and the female portion prevents relative movement ofthe first stent and the second stent.
 24. A stent joining means forjoining a first endoluminal stent to a second endoluminal stentcomprising:a first stent including a radially inwardly compressible maleengaging portion, having a first graft layer disposed externally of saidmale engaging portion; and a second stent including a female portioncooperating at a distal end with a proximal end of said male engagingportion and having a second graft layer disposed externally of saidfemale cooperating portion and which folds over the distal end of saidfemale engaging portion to form an inner sleeve which contacts saidfirst graft layer to form a substantially blood-tight seal; wherein themale engaging portion can be entered into the female portion in aradially compressed state and thereafter caused or allowed to expand inthe female cooperating portion and wherein the inter-engagement of thefirst graft layer of the male engaging portion and the inner sleeve ofthe female cooperating portion resists longitudinal separation of thefirst stent from the second stent.